Base-borate reactor safety spray solution for radiolytic hydrogen suppression

ABSTRACT

As a new composition of matter, water or an aqueous solution of sodium hydroxide containing up to 3,000 ppm boron as the borate is provided, said water or solution having a pH in the range 5.8 to 12.1, said water or solution containing a reagent selected from the group consisting essentially of Na2MoO4, Na2CrO4, Na2WO4, and NaVO3 at a concentration which is effective to suppress hydrogen formation resulting from irradiation of said solution in a nuclear reactor.

llnited States Patent [151 3,691,084 Zittel et al. Sept. 12, 1972 [54] BASE-BORATE REACTOR SAFETY [56] References Cited SPRAY SOLUTION FOR RADIOLYTIC UN D T P HYDROGEN SUPPRESSION [TE 8 A TES ATENTS [72] Inventors: Herman E. Zittel, Kingston; gi siiverman "23/2 R Sebastian B. pi a a l 9 S1 verman Lamont Bate Cfinton an of 3,630,942 12/1971 Soldano ..252/l88 Tenn. I Primary Examiner-Leon D. Rosdol [73] Assignee: The United States of America as Assistant Examiner h-win Gluck AiP' -f 'g C the igs f States Attorney-Roland A. Anderson omic nergy 0mm ion [22] Filed: April 19, 1971 [57] ABSTRACT [21] Appl. No.: 135,393, As a new composition of matter, water or an aqueous solution of sodium hydroxide containing up to 3,000 ppm boron as the borate is provided, said water or [52] US. Cl .I fglfi2;6g2,22535:)89 Solution having a pH in the range 58 to 12'! said 511' int. Cl .3015 47/06,G2 lc 15/18 water mining reagent Selected 58 Field of Search ..2s2/1s2, 188; 176/38, 92 R; the gmup nsisling essentially of M s Nagcroi, 23/2 210 309 Na,WO and NaVO at a concentration which is effective to suppress hydrogen formation resulting from irradiation of said solution in a nuclear reactor.

2 Claims, No Drawings BASE-BORATE REACTOR SAFETY SPRAY SOLUTION FOR RADIOLYTIC HYDROGEN SUPPRESSION BACKGROUND OF THE INVENTION The invention described herein was made in the course of, or under, a contract with the U. S. Atomic Energy Commission.

The present invention relates to an improved reactor safety spray solution. More particularly, it relates to reactor safety spray solutions having an enhanced capacity to suppress the formation of hydrogen produced by exposure of aqueous solutions to the effects of heat and nuclear radiation.

Nuclear plant designs for boiling-water and pressurized-water reactors provide for aqueous sprays or solutions for pressure suppression in the event of a loss of-coolant accident and for concomitant reduction of airborne radioactivity in the reactor containment. It has been determined that these aqueous sprays or solutions would be exposed to as much as 3 X 10 rads of ionizing radiation at temperatures from ambient up to as much as 150 C. during the course of a loss-of-coolant accident. In static and dynamic radiolytic studies involving exposure of water and base-borate solutions, it has been found that considerable quantities of hydrogen and oxygen are generated to a point where they may pose a safety hazard arising from detonation of an explosive mixture of radiolytically generated hydrogen and oxygen.

It is therefore an object of the present invention to provide a method and composition for suppressing the generation of radiolytic hydrogen generated by exposure of water and base-borated solutions comprising a 0.2 M solution of an alkali metal hydroxide containing from 0 to 3,000 ppm boron, said solution having a pH in the range 4 to 10.

SUMMARY AND DESCRIPTION OF THE INVENTION EXAMPLE I The effectiveness of the class of designated reagents in suppressing the formation of hydrogen generated by radiolysis of a base-borate solution is summarized in Table 1 below.

TABLE I Effect of Various Salts on G(I-I in Spray Solutions 0.15 N NaOI-I with 3000 ppm B plus added salt Total dose: 7 X rad Test solution:

Gal/liquid ratio: 1 Cover gas: air Temperature: ambient Additive Radiolytic Compound Concentration H, G( 11,)

(vol Blank l 34 0.43 Blank 2" 37 0.46 Na MoO 2 X 10' 18 0.22 2 X 10" 28 0.35 2 X 10" 34 0.42 2 X 10 35 0.44 Na,CrO, 2 X 10' 14 0.17 2 X 10" 23 0.29 2 X 10* 33 0.41 2 X 10" 37 0.46 Na -W0 2 X 10" 24 0.30 2 X 10" 32 0.40 2 X 10" 33 0.41 2 X 10" 34 0.42 NaVO; 2 X 10' 0.04 2 X 10' 4 0.05 2 X 10" 10 0.12 2 X10 26 0.32 2 X [0" 27 0.34 No salt added.

"Percent of gas phase, measured by volume.

G(H,) no. of moles of H generatedldose, generally in tenns of millimoles H lml of solution/rad of absorbed radiation. 4

It is seen that all of the reagents were effective in suppressing hydrogen formation at the higher range of reagent concentration tested. Of the four reagents tested, sodium vanadate was the most effective at all concentrations. A concentration of 2 X 10' M NaVO in the base-borate solution resulted in a reduction of from 88 to 90 percent relative to the control or blank (without hydrogen suppressant reagent). Concentrations beyond 2 X 10' M do not provide any additional practical increment of hydrogen suppression.

EXAMPLE II In another study, the effect of radiation dose on the hydrogen suppression action of the most efiective reagent was determined over a dose in the range 2.6 X 10 to 4.5 X 10 rads at constant NaVO concentration. The results are summarized in Table II below.

TABLE II Dose Versus G(H in NaOH-H BO -Navo Solution Test solution: 0.15 N NaOI-l-3000 ppm 13 added as H plus 2 X 10 M NaVO Dose rate: 4 X 10' r/hr Gas/liquid ratio: =1 Cover gas: air Test method: capsule Radiolytic Gas Total Dose Gage Pressure G(H (rads) (atm) 2.6 X 10 0.07 0.04 7.3 X 10' 0.12 0.04 1.0 X 10 0.20 0.05, 1.8 X 10 0.32 0.05,, 3.6 X 10 1.74 0.14 4.5 X 10 2.86 0.18,

The data show that the NaVO limits the radiolytic hydrogen production to a fairly constant level up to a dose of about 2 X 10 rads, after which the G(I-I value rises, indicating a relatively slight diminution in hydrogen suppression.

EXAMPLE III This example demonstrates the effectiveness of NaVO, in reducing the amount of hydrogen generated in distilled water. The test conditions as well as test results obtained at two temperatures are summarized in Table III below.

TABLE III Effect of NaVO on Radiolytic H in Distilled H O Test solutions: (A) distilled H O (B) distilled H O plus 2 x 10* M NaVO Gas/liquid ratio": 0.5 Cover gas: air Total dose: 5 X 10 rad Test mode: circulating radiation loop Pumping speed: such that average residence time in radiation capsule between I and 2 mins.

Test Solution Temperature, "C. H,, vol.

A 65 32 B 65 3.7 A 95 23 B 95 2.6

' Ratio of volume of cover gas (air) to volume of liquid in test containment.

"Established by gas chromatograph after system reached steady state as evidenced by constant pressure.

The results show clearly that radiolytic hydrogen is suppressed in a circulating loop of distilled water by the use of an effective concentration of NaVO EXAMPLE IV In order to test the stability of response of the NAAVO; hydrogen suppression action as a function of pH of test solutions, base-borate test solutions containing 2 X 10 M NaVO a wide range of pH were irradiated and tested for the amount of radiolytic hydrogen produced. pH was adjusted by addition of l M NaOH to 2 X10 M NaVO -3,000 ppm boron solution. The results are summarized in Table IV below.

TABLE IV Effect of pH on NaVO G(H Reduction Test solution: 2 X 10' M NaVO 3000 ppm B NaOl-l (used as needed to reach the desired pH) Test mode: static capsule Total dose: l X rad Dose rate: 4 X lo r/hr Temperature: ambient P U 2)" 5.8 0.12 6.5 0.08 7.0 0.05 7.5 0.03 8.0 0.03 8.5 0.04 9.0 0.03 9.5 0.04 10.9 0.22 12.1 0.27

All G(H,) values are averages of three runs.

The test results show clearly that the hydrogen suppression is substantially stable over the pH range 6.5-9.5 and is still significantly effective over a wide range from 5.8 to 12.1.

EXAMPLE V The effect of temperature on the hydrogen suppression efiect of NaVO for dynamic test conditions measured at temperatures in the range 35-125 C. is summarized in Table V below.

TABLE V Effect of NaVO on Radiolytic H Test solutions: (A) 0.15 N NaOH-3000 ppm B (B) 0.15 NaOH-3000 ppm B plus 2 X IO M NaVO,

Cover gas: air

Total dose: ==2 X 10 rad Test mode: radiation loop Test Solution Temperature, C. G( H,)

A 35 0.41 B 35 0.03 A 65 0.36 B 65 0.04 A 0.35 B 95 0.04 A 0.30

The results of the same test conducted at ten times the dose used in compiling the date of Table V are shown in Table VI below.

TABLE VI Effect of NaVO on Radiolytic H Test solutions: (A) 3000 ppm B tiveness of NaVO in suppressing radiolytic hydrogen at elevated temperatures and at high radiation dosage.

In summary, we have described an invention supported by experimental test data which show the effectiveness of a class of reagents which function to suppress the formation of radiolytic hydrogen of irradiated aqueous base-borate solutions or water. Of the class of reagents, NaVO has been shown to be the most effective on a weight basis and effective at elevated temperatures as well as over a wide range of dosage and pH. All irradiation were conducted by exposing the test solutions to a 60,000-curie C0 gamma source.

It will be evident by those skilled in the art that the hydrogen suppression data obtained by irradiating the test solutions with Co gamma provides a sound basis for illustrating the utility of these reagents in suppressing hydrogen in solutions exposed to the radiation of a going nuclear reactor or other radiation which generates sufficient hydrogen to warrant utilizing the hydrogen suppressant action of the defined class of reagents.

What is claimed is:

1. As a new composition of matter, water or an aqueous solution of sodium hydroxide containing up to 3,000 ppm boron as the borate, said water or solution having a pH in the range 5.8 to 12.1, said water or solution containing a reagent selected from the group consisting of Na MoO Na CrO Na WO and NaVO at a concentration of to 2 X 10' M which is effective to suppress hydrogen formation resulting from irradiation of said solution in a nuclear reactor.

2. As a new composition of matter, water or an aqueous solution of sodium hydroxide containing up to 3,000 ppm boron as the borate, said water or solution having a pH in the range 5.8 to 12.1, said water or solution containing sodium vanadate, NaVO at a concentration of 10 to 2 X 10" M which is effective to suppress hydrogen formation resulting from irradiation of said solution by exposure of said water or solution to a radiation dose sufficient to produce hydrogen such as in a nuclear reactor. 

2. As a new composition of matter, water or an aqueous solution of sodium hydroxide containing up to 3,000 ppm boron as the borate, said water or solution having a pH in the range 5.8 to 12.1, said water or solution containing sodium vanadate, NaVO3, at a concentration of 10 6 to 2 X 10 3 M which is effective to suppress hydrogen formation resulting from irradiation of said solution by exposure of said water or solution to a radiation dose sufficient to produce hydrogen such as in a nuclear reactor. 